The neurodegenerative diseases, Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC) are typically diagnosed only after behavioral deficits can be detected clinically (Arasaki and Tamaki, 1998; Leenders et al., 1990; Whitehouse et al., 1982). In Alzheimer's disease, neurons are lost from various regions of the cerebral cortex and hippocampus and manifest as the loss of cognitive functions (Odle, 2003). Parkinson's disease involves the degeneration of select portions of the nigral striatal system (Schapira and Olanow, 2003). Initially, terminal projections of dopamine-containing neurons are lost. Eventually, the cell bodies of the dopaminergic neurons are lost from the substantia nigra (SN). This outcome results in disturbance of motor control and induces tremor, hypokinesia and rigidity (Dauer and Przedborski, 2003). Amyotrophic lateral sclerosis at endstage is characterized by the progressive loss of spinal and cortical motor neurons controlling motor function, particularly the diaphragm (Rowland and Shneider, 2001), resulting in paralysis and death.
In each of the aforementioned diseases, relatively specific neuronal populations degenerate and result in particular behavioral outcomes. It is believed that AD, PD, and ALS are distinct diseases, arising from distinct etiologies and resulting in mutually exclusive behavioral and neuropathological outcomes. This view is based on differential primary symptoms and pathological findings. However, more recent work has pointed to considerable cross-over between the neurodegenerative diseases (see Caine and Eisen, 1989; Muchowski and Wacker, 2005). For example, both PD and ALS patients can exhibit a decline in cognitive function which is conventionally an AD attribute (Aarsland et al., 2003; Vaphiades et al., 2002). Also, AD patients can experience tremors, which is a feature primarily associated with PD (Yokoyama et al., 2002). Another overlap between AD and PD is that the gait disturbances experienced by some PD patients are a predictor for developing AD-like dementia (Verghese et al., 2002). ALS and PD have been shown to overlap significantly, and ALS cases with dementia and/or parkinsonism features are accordingly called ALS-plus (Zoccolella et al., 2002).
Assessments of post-mortem AD, PD, and ALS tissue have also uncovered many similarities between these disease states. In particular, the similarities in the molecular mechanisms associated with protein folding and aggregation have been gaining increasing attention (Muchowski and Wacker, 2005). Although the specific proteins that aggregate in particular neurodegenerative diseases are often unrelated in primary amino acid sequence, the characteristic lesions of AD, PD, and ALS typically contain fibrillar, amyloid-like structures with similar biochemical features (Dobson, 2003). However, instances of proteinacious inclusions possessing a common primary amino acid sequence have been observed across disease classifications. For example, neurofibrillary tangles (NFT) which are primarily associated with AD have been identified in some ALS (Kokubo et al., 2000) and PD (Arima et al., 1999) patients. On the same note, α-synuclein, first identified in the amyloid plaques of AD patients, has also been identified in PD Lewy bodies and Lewy neurites (Lucking and Brice, 2000).
Although the age-related diseases, AD, PD and ALS have similarities, the similarities are limited. In contrast, the neurological disease, amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC) is characterized by a wide range of behavioral and neuropathological attributes shared with each of the age-related diseases and many other neurological diseases. ALS-PDC can express as the classical form of ALS or as a form of parkinsonism with AD features. Moreover, some ALS-PDC patients of Guam or Rota have been observed to present with a combination of these symptoms (Steele and Guzman, 1987). Accordingly, it is believed that understanding ALS-PDC will result in a better understanding of neurological diseases as a whole.
In order to better understand the underlying neurological mechanisms of these disease states at both a cellular level and at the biochemical level, as well as, at the level of the whole animal, animal models of neurodegenerative diseases are needed. Ideally, the animals should display symptoms that approximate the symptoms displayed by humans suffering from these neurodegenerative diseases. The inventors have discovered such animal models and methods for monitoring neurodegenerative diseases in animals using neurotoxic sterol glycosides or neurotoxic glycolipids, or combinations thereof. These neurotoxic sterol glycosides or neurotoxic glycolipids, or combinations thereof, can also be used in combination with neurotoxicity-modulating chromenols.
A non-limiting list of illustrative neurodegenerative diseases that can be modeled using the compositions, methods and models described herein includes amyotrophic lateral sclerosis, early onset Parkinson's disease, late onset Parkinson's disease, Alzheimer's disease, and the like.
In one embodiment, described herein an animal model of a neurodegenerative disease is provided. The animal model comprises a non-human animal in contact with a neurotoxic compound of formula
wherein
R1 is optionally substituted glycosyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, or OR4;
R3 is hydrogen, alkyl, alkenyl, heteroalkyl, haloalkyl, or OR4;
R4 is in each instance independently selected from the group consisting of hydrogen, alkyl, heteroalkyl, haloalkyl, alkenyl, alkynyl, and acyl;
the bonds labeled a, a′, b, c, d, e, f, and g are each independently selected from the group consisting of a single bond and a double bond, with the proviso that for the bonds labeled b, c, and d, adjacent bonds are not both double bonds; and wherein the neurotoxic compound is not a compound selected from the group consisting of β-sitosterol-β-D-glucoside and cholesterol glucoside.
In another embodiment, described herein an animal model of a neurodegenerative disease is provided. The animal model comprises a non-human animal in contact with a neurotoxic compound of formula
wherein R7 and R8 are each independently selected from the group consisting of saturated fatty acid acyl, monounsaturated fatty acid acyl and polyunsaturated fatty acid acyl, each of which is optionally substituted with halogen, methyl, alkyl, hydroxyl, keto, methoxy, or alkoxyl; and R9 is glycosyl.
In another embodiment, described herein an animal model of a neurodegenerative disease is provided. The animal model comprises a non-human animal in contact with a neurotoxic compound of formula
and a neurotoxicity modulating compound of formula
wherein
R1 is optionally substituted glycosyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, or OR4;
R3 is hydrogen, alkyl, alkenyl, heteroalkyl, haloalkyl, or OR4;
R4 is in each instance independently selected from the group consisting of hydrogen, alkyl, heteroalkyl, haloalkyl, alkenyl, alkynyl, and acyl;
the bonds labeled a, a′, b, c, d, e, f, and g are each independently selected from the group consisting of a single bond and a double bond, with the proviso that for the bonds labeled b, c, and d, adjacent bonds are not both double bonds;
R10 and R11 are each independently selected from the group consisting of alkyl and alkenyl, each of which is optionally substituted;
X is from 0 to 3 substituents selected from the group consisting of halogen, alkyl, and alkoxyl; and wherein the neurotoxic compound is not a compound selected from the group consisting of β-sitosterol-β-D-glucoside and cholesterol glucoside.
In another embodiment, an animal model of a neurodegenerative disease is provided. The animal model comprises a non-human animal in contact with a neurotoxic compound of formula
a neurotoxicity modulating compound of formula
wherein R7 and R8 are each independently selected from the group consisting of saturated fatty acid acyl, monounsaturated fatty acid acyl and polyunsaturated fatty acid acyl, each of which is optionally substituted with halogen, methyl, alkyl, hydroxyl, keto, methoxy, or alkoxyl; R9 is glycosyl; R10 and R11 are each independently selected from the group consisting of alkyl and alkenyl, each of which is optionally substituted; and X is from 0 to 3 substituents selected from the group consisting of halogen, alkyl, and alkoxyl is described.
In another embodiment, a method of monitoring a neurodegenerative disease in a non-human animal is provided. The method comprises the steps of administering to the non-human animal a composition comprising a neurotoxic compound of formula
wherein
R1 is optionally substituted glycosyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, or OR4;
R3 is hydrogen, alkyl, alkenyl, heteroalkyl, haloalkyl, or OR4;
R4 is in each instance independently selected from the group consisting of hydrogen, alkyl, heteroalkyl, haloalkyl, alkenyl, alkynyl, and acyl;
the bonds labeled a, a′, b, c, d, e, f, and g are each independently selected from the group consisting of a single bond and a double bond, with the proviso that for the bonds labeled b, c, and d, adjacent bonds are not both double bonds; and wherein the compound is not a compound selected from the group consisting of β-sitosterol-β-D-glucoside and cholesterol glucoside; and monitoring the neurodegenerative disease in the non-human animal.
In another embodiment, a method of monitoring a neurodegenerative disease in a non-human animal is provided. The method comprises the steps of administering to the non-human animal a composition comprising a neurotoxic compound of formula
wherein
R7 and R8 are each independently selected from the group consisting of saturated fatty acid acyl, monounsaturated fatty acid acyl and polyunsaturated fatty acid acyl, each of which is optionally substituted with halogen, methyl, alkyl, hydroxyl, keto, methoxy, or alkoxyl; R9 is glycosyl; and monitoring the neurodegenerative disease in the non-human animal.
In another embodiment, the method of any one of the preceding embodiments wherein the composition further comprises a neurotoxicity modulating compound is provided. The neurotoxicity modulating compound is of formula
wherein
R10 and R11 are each independently selected from the group consisting of alkyl and alkenyl, each of which is optionally substituted; and X is from 0 to 3 substituents selected from the group consisting of halogen, alkyl, and alkoxyl.
In another embodiment, a neurotoxic composition for use in a model of a neurodegenerative disease is provided. The neurotoxic composition comprises a compound of formula
wherein
R1 is optionally substituted glycosyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, or OR4;
R3 is hydrogen, alkyl, alkenyl, heteroalkyl, haloalkyl, or OR4;
R4 is in each instance independently selected from the group consisting of hydrogen, alkyl, heteroalkyl, haloalkyl, alkenyl, alkynyl, and acyl;
the bonds labeled a, a′, b, c, d, e, f, and g are each independently selected from the group consisting of a single bond and a double bond, with the proviso that for the bonds labeled b, c, and d, adjacent bonds are not both double bonds; and wherein the compound is not a compound selected from the group consisting of β-sitosterol-β-D-glucoside and cholesterol glucoside; and a pharmaceutically acceptable carrier therefore.
In another embodiment, a neurotoxic composition for use in a model of a neurodegenerative disease is provided. The neurotoxic composition comprises a compound of formula
wherein
R7 and R8 are each independently selected from the group consisting of saturated fatty acid acyl, monounsaturated fatty acid acyl and polyunsaturated fatty acid acyl, each of which is optionally substituted with halogen, methyl, alkyl, hydroxy, keto, methoxy, or alkoxyl; R9 is glycosyl; and a pharmaceutically acceptable carrier therefore.
In another embodiment, the neurotoxic composition of any one of the preceding embodiments further comprising a neurotoxicity modulating compound is provided. The neurotoxicity modulating compound is of formula
wherein
R10 and R11 are each independently selected from the group consisting of alkyl and alkenyl, each of which is optionally substituted; and X is from 0 to 3 substituents selected from the group consisting of halogen, alkyl, and alkoxyl.
In another embodiment, a compound for use in a model of a neurodegenerative disease is provided. The compound has the formula
wherein
R1 is optionally substituted glycosyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, or OR4;
R3 is hydrogen, alkyl, alkenyl, heteroalkyl, haloalkyl, or OR4;
R4 is in each instance independently selected from the group consisting of hydrogen, alkyl, heteroalkyl, haloalkyl, alkenyl, alkynyl, and acyl;
the bonds labeled a, a′, b, c, d, e, f, and g are each independently selected from the group consisting of a single bond and a double bond, with the proviso that for the bonds labeled b, c, and d, adjacent bonds are not both double bonds; and wherein the compound is not a compound selected from the group consisting of β-sitosterol-β-D-glucoside and cholesterol glucoside.
In another embodiment, a method for examining neurodegeneration in a non-human animal is provided. The method comprises the step of administering a synthetic neurotoxic sterol glycoside to the animal, wherein the neurotoxic sterol glycoside causes the neurodegeneration in the animal, and wherein the neurodegeneration in the animal is examined by observing behavioral abnormalities in the animal or is examined post-mortem in a central nervous system tissue of the animal. Illustratively, the sterol glycoside can be any of the above-described sterol glycoside neurotoxic compounds, or combination thereof, or any of these compounds in combination with any of the neurotoxicity modulating compounds described above, and the compounds can be isolated (e.g., greater than 90%, 95%, 96%, 97%, 98%, 98.5%, 99%, 99.5%, or 99.7% pure). In all of the above-described embodiments, the neurological degeneration can be identified by a behavioral test selected from the group consisting of a leg extension test, a gait length test, a rotarod test, a wire hang test, a water maze test, a radial arm maze test, a Digigate system test, an Ethovision test, an anxiety test, a depression test, and an olfactory system test. In one aspect, the behavioral abnormality can be an abnormality in motor function or an abnormality in cognitive function. Further, illustratively, the central nervous system tissue examined post-mortem can be from a site selected from the group consisting of the cortex, the hippocampus, the spinal cord, and the substantia nigra. Illustratively, the sterol glycoside can cause neuronal excitotoxicity.
In yet another embodiment, an animal model of neurotoxic sterol glycoside-induced neurodegeneration is provided. The animal model comprises a non-human animal having neurodegeneration caused by administration of a neurotoxic sterol glycoside in an amount sufficient to cause the neurodegeneration in the non-human animal. Illustratively, the sterol glycoside can be any of the above-described neurotoxic compounds, or combination thereof, or the sterol glycoside can be in combination with any of the neurotoxicity modulating compounds described above, and the compounds can be isolated (e.g., greater than 90%, 95%, 96%, 97%, 98%, 98.5%, 99%, 99.5%, or 99.7% pure) and can be synthetic. In this embodiment, the neurological degeneration can be identified by a behavioral test selected from the group consisting of a leg extension test, a gait length test, a rotarod test, a wire hang test, a water maze test, a radial arm maze test, a Digigate system test, an Ethovision test, an anxiety test, a depression test, and an olfactory system test. In one aspect, the behavioral abnormality can be an abnormality in motor function or an abnormality in cognitive function. Further, illustratively, the central nervous system tissue examined post-mortem can be a site selected from the group consisting of the cortex, the hippocampus, the spinal cord, and the substantia nigra. Illustratively, the sterol glycoside can cause neuronal excitotoxicity.
In any of the embodiments described herein, a glycosidic bond in the sterol glycoside can be hydrolyzed prior to administration of the compound to the animal, for example, to determine if hydrolysis of the bond inhibits the neurotoxicity of the sterol glycoside. In these embodiments, the sterol glycoside can be treated with an enzyme that degrades the neurotoxic sterol glycoside prior to administration of the sterol glycoside to the animal. In any of the embodiments described in the application, the sterol glycoside can be non-acylated.
In another embodiment the purity of any of the above-described compounds the compound is greater than 90%, 95%, 96%, 97%, 98%, 98.5%, 99%, 99.5%, or 99.7% pure. Such pure compounds are isolated compounds. In any of the embodiments described herein, the compounds can be synthetic.
In another embodiment, a compound for use in a model of a neurodegenerative disease is provided. The compound has the formula
wherein
R7 and R8 are each independently selected from the group consisting of saturated fatty acid acyl, monounsaturated fatty acid acyl and polyunsaturated fatty acid acyl, each of which is optionally substituted with halogen, methyl, alkyl, hydroxy, keto, methoxy, or alkoxyl; R9 is glycosyl.
In another embodiment, the purity of the compound described in the preceding paragraph is greater than 90%, 95%, 96%, 97%, 98%, 98.5%, 99%, 99.5%, or 99.7% pure. Such pure compounds are isolated compounds. In any of the embodiments described herein, the compounds can be synthetic.
In another embodiment, a neurotoxicity modulating compound is provided. The neurotoxicity modulating compound has the formula
wherein
R10 and R11 are each independently selected from the group consisting of alkyl and alkenyl, each of which is optionally substituted; X is from 0 to 3 substituents selected from the group consisting of halogen, alkyl, and alkoxyl.
In another embodiment, the purity of the compound described in the preceding paragraph is greater than 90%, 95%, 96%, 97%, 98%, 98.5%, 99%, 99.5%, or 99.7% pure. Such pure compounds are isolated compounds. In any of the embodiments described herein, the compounds can be synthetic.
In another embodiment, a neurotoxic composition for use in a fetal exposure model of a neurodegenerative disease is described. The neurotoxic composition comprises a compound of formula
wherein
R1 is optionally substituted glycosyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, or OR4;
R3 is hydrogen, alkyl, alkenyl, heteroalkyl, haloalkyl, or OR4;
R4 is in each instance independently selected from the group consisting of hydrogen, alkyl, heteroalkyl, haloalkyl, alkenyl, alkynyl, and acyl;
the bonds labeled a, a′, b, c, d, e, f, and g are each independently selected from the group consisting of a single bond and a double bond, with the proviso that for the bonds labeled b, c, and d, adjacent bonds are not both double bonds; wherein the non-human animal is a fetal animal; and a pharmaceutically acceptable carrier therefore.
In another embodiment, a neurotoxic composition for use in a model of a neurodegenerative disease is described. The neurotoxic composition comprises a compound of formula
wherein
R7 and R8 are each independently selected from the group consisting of saturated fatty acid acyl, monounsaturated fatty acid acyl and polyunsaturated fatty acid acyl, each of which is optionally substituted with halogen, methyl, alkyl, hydroxy, keto, methoxy, or alkoxyl; R9 is glycosyl; and a pharmaceutically acceptable carrier therefore.